Grunner: implement homing

Signed-off-by: David Jander <djander@gmail.com>
Add preliminary support for hwmon temperature sensor

Added support for reading temperature from a 100k thermistor connected via
an opamp to a hwmon-based ADC

Signed-off-by: David Jander <djander@gmail.com>
GPIO: Added support for GPIO outputs

Signed-off-by: David Jander <djander@gmail.com>
audiodev: added set_position and get_position

Signed-off-by: David Jander <djander@gmail.com>